The present invention generally relates to a sheet wrapping package inspecting device which detects a mingled foreign substance, damage, and/or dirt of a tablet, which may occur during a sheet wrapping process for wrapping the tablet by checking an appearance thereof without contact thereto. More particularly, it relates to a sheet wrapping package inspecting device which observes both the reflected ray and transmitted ray through a TV camera.
In this specification, the term xe2x80x9ctablet inspection,xe2x80x9d unless otherwise specified, generally covers the inspection of a sheet wrapping package which includes a tablet and its wrapping/packaging (hereinafter simply referred to as xe2x80x9cwrappingxe2x80x9d) sheet, and detecting a foreign substance in a space of so-called pocket of the wrapping sheet where the tablet is placed. Also, the term xe2x80x9csheet wrapping package inspectingxe2x80x9d is widely used to cover the inspection of a part of the object to be wrapped and its wrapping sheet, and a defect inspection for detecting a foreign substance contained in a space of so-called pocket of the wrapping sheet where the part of the object to be wrapped is placed. In addition, the whole object to be inspected, including the part of the object such as the tablet and its wrapping sheet, is simply referred to as a xe2x80x9cwrapping sheet,xe2x80x9d which is distinguished from a xe2x80x9csheet portion (i.e., a sheet),xe2x80x9d unless otherwise specified.
A conventional tablet inspection, which is one of the important sheet wrapping package inspections, will be explained herein below.
A portion to be subjected to the tablet inspection is roughly classified into a tablet, a sheet portion for wrapping the tablet, and a so-called pocket for carrying and holding the tablet therein. As for the tablet, checked by the inspection are a character and/or a symbol formed on the tablet, and a crack, split, fold, breakage, dirt, stain, and adhesive of the tablet. As for the sheet portion and the pocket, checked by the inspection are a stain and dirt thereof, a foreign substance, a broken piece of the tablet, a hair, and a fiber mingled during the wrapping process. It is also checked by the inspection whether or not a different tablet is mistakenly contained in the wrapping.
On the other hand, prior to the present invention, two methods, a method called a reflection type and a method called a transmission type, have been considered separately as an individual method of the inspection. In the reflection type inspection method, a ray is emitted to a wrapping sheet from the upper side thereof, and the reflected ray is observed by a TV camera disposed above the wrapping sheet to detect a defect. In the transmission type method, a ray is emitted to the wrapping sheet from the lower side thereof, or the rear side thereof, and the transmitted ray is observed by a TV camera to detect a defect. According to the reflection type method, it is possible to check the shape of the tablet and detect a foreign substance on the tablet and/or a foreign substance mingled in the wrapping sheet. On the other hand, the transmission type method is utilized to detect a foreign substance mingled in the wrapping sheet and check the shape of the tablet.
As mentioned above, two types of conventional tablet inspection methods, i.e., the reflection type method and the transmission type method, have been considered. However, these conventional methods have the following serious drawbacks.
In the reflection method, many highlights are often captured at the pocket because of the multiple reflection effect, the specular reflection effect and the concave-reflector effect, and thus those highlights are detected as false defects. To escape from those phenomena, the pocket were excluded from the object to be inspected by taking a logical mask covering the region of the image corresponding the pocket on the image by detecting the pocket primarily. This causes serious problems in that not only the detection of the pocket is troublesome but also the inspection of the pocket cannot be performed due to the logical mask.
Also, the surface of the sheet somewhat includes the element of the specular reflection, and the element sometimes appears as a highlight on the image. Although highlights appearing on the pocket and the sheet surface produce serious errors as false defects, there have not been any ways to distinguish and exclude such false defects.
In the transmission method, the contrast of a thin foreign substance such as a hair becomes quite low on the transmitted ray image because of diffraction and some other reasons. This causes a serious omission in detecting defects. Further, it is not possible to distinguish whether a defect mingled in the sheet is a broken piece of the tablet or a foreign substance such as dust, although it is one of the most important issues of the inspection.
As mentioned above, it has not been possible to distinguish and detect serious defects including all defects constantly by either method.
Furthermore, even the combination of these methods could not detect every defects precisely across whole regions at all.
The objective of the present invention is to provide the sheet wrapping package inspecting device that solves the above-mentioned problems and can easily and precisely detect all defects including defects in the pocket.
The sheet wrapping package inspecting device according to the present invention includes a light source and a two-dimensional sensor located above a wrapping sheet respectively, means for inputting a reflected ray image above the wrapping sheet and a light source located below the sheet wrapping and means for inputting a transmitted ray image. The device plots a plurality of several binary or multi-value images of the gained reflected ray image and transmitted ray image, creates density code distribution maps of those images, and thereafter detects defects such as a mingled foreign substance, a damage and/or dirt of a part of a whole object to be inspected, the wrapping sheet and the pocket according to the code distribution maps.
In addition, also disclosed herein is a defect discrimination method in which a logical operation between images have been performed to discriminate a defect based on the logical operation results.
In addition, the device detects a defect by dividing the inputted image into several regions according to the brightness distribution or the code distribution of the inputted image and thereafter giving a code of the neighboring region as an auxiliary code to the code value of each divided region.
To prevent the omission of detecting a defect, the device is provided with a half-mirror or a reflection mirror that reflects at least five percent (%) of the incident light; the reflector is located right under the wrapping sheet.
On the other hand, to enhance the inspection efficiency, the device includes:
light means including light sources located above and below a wrapping sheet, the light sources having different color spectra, or light means including light sources located above and below the wrapping sheet and color filters located between the wrapping sheet and each light source, respectively, the color filters having different color spectra; and
two-dimensional sensor located above the wrapping sheet,
wherein a two dimension image is inputted while the light sources on both sides of the wrapping sheet are illuminated simultaneously, and the reflected ray image and the transmitted ray image are separated according to the color spectrum of each image because the color spectrum corresponds to that of each light source.
Furthermore, the device separates the reflected ray image and the transmitted ray image by removing the common wavelength element of both the light sources by placing color filters that transmit the same wavelength as the transmittance wavelength spectrum.
Also, as a method of detecting a defect without separating the reflected ray image and the transmitted ray image, the way of detecting defects by adjusting the ratio of the reflected ray and the transmitted ray with a dimmer, and inputting and multi-valuing images of such rays are applicable.